Thermosetting polymers have myriad uses in various industries including aerospace and electronics industries as well as in the manufacture of consumer products. In particular, thermosets have the properties of being durable and relatively resistant to environmental stressors such as heat, microorganisms, and water. As a result, thermosetting polymers have found wide ranging uses as coatings; adhesives; construction components such as for crack repair, bonding and grouting; and in medical and dental applications such as in bone cements and implants.
However, thermosetting polymers are often highly cross-linked, adding to stability but increasing brittleness. Dental polymers are prime examples of highly crosslinked, brittle thermosets. Linear polymers can serve as highly effective thermoplastic toughening agents in brittle thermosetting resins (Hodgkin et al., Thermoplastic toughening of epoxy resins: a critical review, Polymers for Advanced Technologies, 9:3-10, 1998). Unfortunately, the inclusion of thermoplastics into such polymers can reduce their elastic modulus at the same time that they enhance ductility.
Similarly, it is often advantageous to include other components in a thermosetting polymer which add desired characteristics to a thermosetting polymer composition. For example, a radiopaque filler is often desirable in a composition including a thermosetting polymer. Radiopacity is useful in numerous fields of use, such as in medical and dental applications where radiography is often used to investigate the status of implanted material. However, such fillers are often incompatible with the polymer. For instance, zirconium offers a significant source of radiopacity in dental composite formulations of thermosetting polymers. Unfortunately, zirconium oxide particles and other metal containing particles have proven difficult to disperse homogeneously into organic resins.
Thus, there is a continuing need for improved polymer composite and nanocomposite compositions, toughening agents and methods for their synthesis.